This application is the national phase under 35 U.S.C. xc2xa7371 of PCT International Application No. PCT/JP99/00163 which has an International filing date of Jan. 19, 1999, which designated the United States of America.
The present invention relates to a method and an apparatus for producing semisolidified metal to obtain predetermined slurry from molten metal.
An operation is generally performed to produce semisolidified metal, i.e., slurry in an amount of one shot for the forming process, by using molten metal of, for example, aluminum, magnesium, or alloy thereof. It is known that a forming operation based on the use of slurry especially has such an advantage that the surface accuracy of a formed product is excellent. In order to produce such slurry, for example, the thixocasting process and the rheocasting process are widely adopted.
However, in the case of the thixocasting process described above, it is necessary to use an exclusive billet and a reheating apparatus. For this reason, the following problems are pointed out. That is, the material cost and the equipment cost are considerably expensive, and the entire production operation is complicated.
On the other hand, in the rheocasting process, the mass production is performed based on the continuous batch system. In this process, the cooling is performed by discharging the molten metal while allowing the molten metal to make contact with a cooling section cooled with water. Therefore, the temperature of slurry differs between the start and the end of the cooling. A problem arises in that the temperature of the slurry is not managed accurately.
A method is also known, in which slurry is produced in accordance with cooling, heating, and agitation in a forming machine. However, the following inconveniences arise. That is, the cycle time is prolonged, and especially the shot weight is increased.
When the produced slurry is supplied into the forming machine, a container for accommodating the, slurry is usually inverted in the vertical direction. However, it is difficult to discharge the entire amount of slurry in the container, for example, due to the temperature of the slurry in the container, the shape of the container, and the weight of the slurry. As a result, the following problems are pointed out. That is, remaining matters of the slurry appear in the container, and the supply weight of the slurry is dispersed. Further, the slurry, which:is newly produced in the container, is badly affected thereby.
When different parts are formed, the shot weight differs depending thereon. Therefore, the following problems are pointed out. That is, it is impossible to correctly manage the temperature of the slurry. When the shot weight is increased, it takes a long time to perform the operation for producing the slurry. It is difficult to efficiently perform the forming operation for a variety of different parts to give high qualities.
An object of the present invention is to provide a method and an apparatus for producing semisolidified metal, which make it possible to produce desired slurry efficiently and economically.
Another object of the present invention is to provide an apparatus for producing semisolidified metal, which makes it possible to economically produce desired slurry and easily discharge the slurry in a reliable manner.
Still another object of the present Invention is to provide an apparatus for producing semisolidified metal, which makes it possible to economically produce various slurries having different weight so that they have high qualities, wherein the system is simplified.
According to the present invention, a predetermined amount of molten metal is supplied to a heat-insulating crucible. After that, the molten metal in the crucible is cooled by the aid of a cooling member which is cooled to be at a predetermined temperature of not more than a temperature of the molten metal. Simultaneously, the molten metal is agitated. Accordingly, in the heat-insulating crucible, the molten metal is reliably formed into slurry generally uniformly as a whole without involving any directivity of cooling. Thus, the reheating is unnecessary, and it is possible to efficiently obtain desired semisolidified metal.
According to the present invention, a predetermined amount of molten metal is supplied to a heat-insulating crucible, and then the molten metal in the crucible is cooled by the aid of a cooling member which is cooled to be at a predetermined temperature of not more than a temperature of the molten metal. Further, the cooling member is moved in the horizontal direction and/or in the vertical direction while rotating the cooling member. Thus, the molten metal is agitated. For example, the cooling member is moved in a reciprocating manner in the horizontal direction and/or in the vertical direction. Alternatively, the cooling member is moved spirally in the horizontal direction.
Accordingly, especially when heat-insulating crucibles having various shapes are used, the cooling member is moved along with the shape of the heat-insulating crucible. Thus, the directivity of cooling is excluded to be as less as possible, and the molten metal can be effectively agitated. Accordingly, the molten metal is formed into slurry uniformly and reliably as a whole. It is possible to obtain desired semisolidified metal efficiently with a high quality.
In the present invention, the semisolidified metal is produced after a predetermined amount of molten metal is supplied to a heat-insulating crucible, by cooling and agitating the molten metal in the heat-insulating crucible by the aid of a plurality of cooling members. Accordingly, even when the shot weight is increased, then the directivity of cooling is avoided to be as less as possible, and it is possible to quickly and smoothly obtain the desired semisolidified metal formed into slurry uniformly and reliably as a whole.
Further, the cooling members are integrally held by a driving mechanism by the aid of a fixing means in a state in which an arbitrary number of the cooling members are stacked with each other. Therefore, it is enough to change the number of stacked cooling members depending on the change of the shot weight. Thus, it is possible to produce the desired semisolidified metal efficiently to have a high quality. The fixing means includes a shaft member for being integrally inserted into the plurality of stacked cooling members, and a fixture for being screwed on an end of the shaft member. Thus, it is possible to effectively simplify the structure.
In the present invention, the molten metal is supplied into a heat-insulating crucible, and then a cooling member is immersed in the molten metal. The molten metal is agitated in a state in which a cooling medium having a predetermined temperature is supplied to the inside of the cooling member. Accordingly, the directivity of cooling is avoided to be as less as possible, and it is possible to convert the molten metal into slurry quickly and reliably. Further, when the temperature of the cooling medium is managed, it is unnecessary to reheat the semisolidified metal. Thus, it is possible to efficiently obtain the desired semisolidified metal.
In the present invention, a predetermined amount of molten metal is supplied to divided type heat-insulating crucibles. After that, the molten metal in the heat-insulating crucibles is cooled and agitated by the aid of a cooling member to produce semisolidified metal. Subsequently, the heat-insulating crucibles are subjected to opening/closing operation by the aid of an opening/closing mechanism. Accordingly, the semisolidified metal in the heat-insulating crucibles falls in accordance with its self-weight, and it is discharged from the heat-insulating crucibles.
Accordingly, the directivity of cooling is avoided to be as less as possible, and it is possible to obtain the desired semisolidified metal formed into slurry uniformly and reliably as a whole. Further, it is possible to discharge the semisolidified metal from the heat-insulating crucibles smoothly and reliably.